Display electrodes and address electrodes of a plasma display panel (PDP) usually include silver having high electroconductivity.
The silver electrode can be made in accordance with various methods. It is generally made by the following process: a paste including silver particles, glass frit, a resin, and a solvent is screen-printed to form a pattern, which is then fired at at least 500° C.
The silver electrode may be ionized to Ag+ during the firing process, and the ions may migrate to an adjacent glass substrate or a dielectric layer through diffusion. Diffused silver ions are reduced by alkali metals such as Sn2+, Na+, or Pb2+ in the glass substrate or dielectric layer. The reduced silver ions are precipitated as colloid particles and grown continuously, resulting in coloring of the glass substrate or dielectric layer. This phenomenon causes yellowing of a PDP panel (J. E. SHELBY and J. VITKO. Jr Journal of Non Crystalline Solids Vo1. 50 1982 107-117).
Such a yellowing phenomenon has an unfavorable effect on display quality of a module, such as on the contrast ratio in a bright room, resulting in deterioration of brightness and chromaticity of a panel. Resultantly, the above phenomena significantly deteriorate the display quality of a PDP.
Furthermore, the silver electrode becomes silver oxide or silver sulfide from external factors such as moisture or impurities. The silver oxide or silver sulfide may be deposited on the electrode surface and cause a poor electrode pattern. In addition, the color of the silver electrode may be changed and it may corrode, resulting in deterioration of life-span as well as electrical characteristics.
There are many approaches to solve the problems, but the problems of corrosion of a silver electrode and yellowing of a glass substrate and a dielectric layer persist.